1. Heat oven to 400 degrees F. Prick potatoes in several places with a fork.
2. Bake potatoes directly on oven racks in 400 degree F oven until tender when pierced, about 45 minutes.
3. When cool enough to handle, cut oval out of top of each potato with paring knife, angling slightly. Reserve tops. Scoop out flesh, leaving 1/4-inch-thick shells; save flesh in large bowl.
4. Peel skin from reserved tops; add tops to potato in bowl. Mash. Stir in sour cream, butter, vinegar, salt and pepper; filling should be stiff. Stir in cheese and scallions. Fill potato shells, mounding. Place in 13 x 9 x 2-inch baking pan. Lightly sprinkle with paprika.
5. Bake in 400 degree F oven 40 to 45 minutes or until golden brown. Serve hot, or let cool and refrigerate, and then reheat.